Wireless communication networks, such as mobile wireless telephone networks, have become increasingly prevalent over the past decade. The wireless telephone networks are commonly referred to as “cellular networks”, because the network infrastructure is arranged to divide the service area into a plurality of regions called “cells”. A terrestrial cellular network includes a plurality of interconnected base stations, or base nodes, that are distributed geographically at designated locations throughout the service area. Each base node includes one or more transceivers that are capable of transmitting and receiving electromagnetic signals, such as radio frequency (RF) communications signals, to and from mobile user nodes, such as wireless telephones, located within the coverage area. The communications signals include, for example, voice data that has been modulated according to a desired modulation technique and transmitted as data packets. As can be appreciated by one skilled in the art, network nodes transmit and receive data packet communications in a multiplexed format, such as time-division multiple access (TDMA) format, code-division multiple access (CDMA) format, or frequency-division multiple access (FDMA) format, which enables a single transceiver at a first node to communicate simultaneously with several other nodes in its coverage area.
In recent years, a type of mobile communications network known as an “ad-hoc” network has been developed and deployed. In this type of network, each mobile node is capable of operating as a base station or router for the other mobile nodes, thus eliminating the need for a fixed infrastructure of base stations.
More sophisticated ad-hoc networks are also being developed and deployed, which, in addition to enabling mobile nodes to communicate with each other as in a conventional ad-hoc network, further enable the mobile nodes to access a fixed network and thus communicate with other mobile nodes, such as those on the public switched telephone network (PSTN), and on other networks such as the Internet.
Because the propagation conditions in mobile networks are time-varying and error-prone, it is challenging to sustain a high system performance in these networks. Therefore, it is desirable to deploy mechanisms that adapt the characteristics of the wireless system to the dynamic changes of the propagation channel based on certain measurements.
In Media Access Control (MAC) layer, three factors play critical roles in adapting the communication to the characteristics of the mobile channel: transmit power, data rate and the transmission duration of a data packet. In relation with the other two elements, the transmit power has a very slow variation and it is considered constant for the time when the teaching of this invention applies. Data rate is characterized as bits per second and is determined by the modulation and coding complexity. The duration of a data packet transmission is the result of the current data rate and the amount of data in a packet.
Accordingly, there is a need for a method and apparatus for determining data rate and packet length in mobile wireless networks.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.